using System.Text.RegularExpressions;

using Dapper;

using Myriad.Cache;
using Myriad.Extensions;
using Myriad.Rest;
using Myriad.Rest.Exceptions;
using Myriad.Types;

using NodaTime;
using NodaTime.Extensions;
using NodaTime.Text;

using PluralKit.Core;

using Serilog;

namespace PluralKit.Bot;

public class LoggerCleanService
{
    private static readonly Regex _basicRegex = new("(\\d{17,19})");
    private static readonly Regex _dynoRegex = new("Message ID: (\\d{17,19})");
    private static readonly Regex _carlRegex = new("ID: (\\d{17,19})");
    private static readonly Regex _circleRegex = new("\\(`(\\d{17,19})`\\)");
    private static readonly Regex _loggerARegex = new("Message = (\\d{17,19})");
    private static readonly Regex _loggerBRegex = new("MessageID:(\\d{17,19})");
    private static readonly Regex _auttajaRegex = new("Message (\\d{17,19}) deleted");

    private static readonly Regex _mantaroRegex =
        new("Message \\(?ID:? (\\d{17,19})\\)? created by .* in channel .* was deleted\\.");

    private static readonly Regex _pancakeRegex = new("Message from <@(\\d{17,19})> deleted in");
    private static readonly Regex _unbelievaboatRegex = new("Message ID: (\\d{17,19})");
    private static readonly Regex _vanessaRegex = new("Message sent by <@!?(\\d{17,19})> deleted in");
    private static readonly Regex _salRegex = new("\\(ID: (\\d{17,19})\\)");
    private static readonly Regex _GearBotRegex = new("\\(``(\\d{17,19})``\\) in <#\\d{17,19}> has been removed.");
    private static readonly Regex _GiselleRegex = new("\\*\\*Message ID\\*\\*: `(\\d{17,19})`");
    private static readonly Regex _ProBotRegex = new("\\*\\*Message sent by <@(\\d{17,19})> deleted in <#\\d{17,19}>.\\*\\*");

    private static readonly Regex _VortexRegex =
        new("`\\[(\\d\\d:\\d\\d:\\d\\d)\\]` .* \\(ID:(\\d{17,19})\\).* <#\\d{17,19}>:");

    private static readonly Dictionary<ulong, LoggerBot> _bots = new[]
    {
        new LoggerBot("Carl-bot", 235148962103951360, fuzzyExtractFunc: ExtractCarlBot), // webhooks
        new LoggerBot("Circle", 497196352866877441, fuzzyExtractFunc: ExtractCircle),
        new LoggerBot("Pancake", 239631525350604801, fuzzyExtractFunc: ExtractPancake),
        new LoggerBot("Logger", 298822483060981760, ExtractLogger), // webhook
        new LoggerBot("Patron Logger", 579149474975449098, ExtractLogger), // webhook (?)
        new LoggerBot("Dyno#3861", 155149108183695360, ExtractDyno, applicationId: 161660517914509312), // webhook
        new LoggerBot("Dyno#7532", 168274214858653696, ExtractDyno), // webhook
        new LoggerBot("Dyno#1390", 470722245824610306, ExtractDyno), // webhook
        new LoggerBot("Dyno#8506", 470722416427925514, ExtractDyno), // webhook
        new LoggerBot("Dyno#0811", 470722753218084866, ExtractDyno), // webhook
        new LoggerBot("Dyno#9026", 470723667303727125, ExtractDyno), // webhook
        new LoggerBot("Dyno#8389", 470724017205149701, ExtractDyno), // webhook
        new LoggerBot("Dyno#5714", 470723870270160917, ExtractDyno), // webhook
        new LoggerBot("Dyno#1961", 347378323418251264, ExtractDyno), // webhook
        new LoggerBot("Auttaja", 242730576195354624, ExtractAuttaja), // webhook
        new LoggerBot("GenericBot", 295329346590343168, ExtractGenericBot),
        new LoggerBot("blargbot", 134133271750639616, ExtractBlargBot),
        new LoggerBot("Mantaro", 213466096718708737, ExtractMantaro),
        new LoggerBot("UnbelievaBoat", 292953664492929025, ExtractUnbelievaBoat), // webhook
        new LoggerBot("UnbelievaBoat Premium", 356950275044671499, ExtractUnbelievaBoat), // webhook (?)
        new LoggerBot("Vanessa", 310261055060443136, fuzzyExtractFunc: ExtractVanessa),
        new LoggerBot("SafetyAtLast", 401549924199694338, fuzzyExtractFunc: ExtractSAL),
        new LoggerBot("GearBot", 349977940198555660, fuzzyExtractFunc: ExtractGearBot),
        new LoggerBot("GiselleBot", 356831787445387285, ExtractGiselleBot),
        new LoggerBot("Vortex", 240254129333731328, fuzzyExtractFunc: ExtractVortex),
        new LoggerBot("ProBot", 282859044593598464, fuzzyExtractFunc: ExtractProBot), // webhook
        new LoggerBot("ProBot Prime", 567703512763334685, fuzzyExtractFunc: ExtractProBot), // webhook (?)
    }.ToDictionary(b => b.Id);

    private static Dictionary<ulong, LoggerBot> _botsByApplicationId
        => _bots.Values.ToDictionary(b => b.ApplicationId);

    private readonly IDiscordCache _cache;
    private readonly DiscordApiClient _client;

    private readonly RedisService _redis;
    private readonly ILogger _logger;

    public LoggerCleanService(RedisService redis, DiscordApiClient client, IDiscordCache cache, ILogger logger)
    {
        _redis = redis;
        _client = client;
        _cache = cache;
        _logger = logger.ForContext<LoggerCleanService>();
    }

    public static ICollection<LoggerBot> Bots => _bots.Values;

    public async ValueTask HandleLoggerBotCleanup(Message msg)
    {
        var channel = await _cache.GetChannel(msg.ChannelId);

        if (channel.Type != Channel.ChannelType.GuildText) return;
        if (!(await _cache.PermissionsIn(channel.Id)).HasFlag(PermissionSet.ManageMessages)) return;

        // If this message is from a *webhook*, check if the application ID matches one of the bots we know
        // If it's from a *bot*, check the bot ID to see if we know it.
        LoggerBot bot = null;
        if (msg.WebhookId != null && msg.ApplicationId != null) _botsByApplicationId.TryGetValue(msg.ApplicationId.Value, out bot);
        else if (msg.Author.Bot) _bots.TryGetValue(msg.Author.Id, out bot);

        // If we didn't find anything before, or what we found is an unsupported bot, bail
        if (bot == null) return;

        try
        {
            // We try two ways of extracting the actual message, depending on the bots
            if (bot.FuzzyExtractFunc != null)
            {
                // Some bots (Carl, Circle, etc) only give us a user ID and a rough timestamp, so we try our best to
                // "cross-reference" those with the message DB. We know the deletion event happens *after* the message
                // was sent, so we're checking for any messages sent in the same guild within 3 seconds before the
                // delete event timestamp, which is... good enough, I think? Potential for false positives and negatives
                // either way but shouldn't be too much, given it's constrained by user ID and guild.
                var fuzzy = bot.FuzzyExtractFunc(msg);
                if (fuzzy == null) return;

                _logger.Debug("Fuzzy logclean for {BotName} on {MessageId}: {@FuzzyExtractResult}",
                    bot.Name, msg.Id, fuzzy);

                var exists = await _redis.HasLogCleanup(fuzzy.Value.User, msg.GuildId.Value);

                // If we didn't find a corresponding message, bail
                if (!exists) return;

                // Otherwise, we can *reasonably assume* that this is a logged deletion, so delete the log message.
                await _client.DeleteMessage(msg.ChannelId, msg.Id);
            }
            else if (bot.ExtractFunc != null)
            {
                // Other bots give us the message ID itself, and we can just extract that from the database directly.
                var extractedId = bot.ExtractFunc(msg);
                if (extractedId == null) return; // If we didn't find anything, bail.

                _logger.Debug("Pure logclean for {BotName} on {MessageId}: {@FuzzyExtractResult}",
                    bot.Name, msg.Id, extractedId);

                var mid = await _redis.GetOriginalMid(extractedId.Value);
                if (mid == null) return;

                // If we've gotten this far, we found a logged deletion of a trigger message. Just yeet it!
                await _client.DeleteMessage(msg.ChannelId, msg.Id);
            } // else should not happen, but idk, it might
        }
        catch (NotFoundException)
        {
            // Sort of a temporary measure: getting an error in Sentry about a NotFoundException from D#+ here
            // The only thing I can think of that'd cause this are the DeleteAsync() calls which 404 when
            // the message doesn't exist anyway - so should be safe to just ignore it, right?
        }
    }

    private static ulong? ExtractAuttaja(Message msg)
    {
        // Auttaja has an optional "compact mode" that logs without embeds
        // That one puts the ID in the message content, non-compact puts it in the embed description.
        // Regex also checks that this is a deletion.
        var stringWithId = msg.Embeds?.FirstOrDefault()?.Description ?? msg.Content;
        if (stringWithId == null) return null;

        var match = _auttajaRegex.Match(stringWithId);
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static ulong? ExtractDyno(Message msg)
    {
        // Embed *description* contains "Message sent by [mention] deleted in [channel]", contains message ID in footer per regex
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Footer == null || !(embed.Description?.Contains("Deleted in") ?? false)) return null;
        var match = _dynoRegex.Match(embed.Footer.Text ?? "");
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static ulong? ExtractLogger(Message msg)
    {
        // Embed contains title "Message deleted in [channel]", and an ID field containing both message and user ID (see regex).
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed == null) return null;
        if (!embed.Description.StartsWith("Message deleted in")) return null;

        var idField = embed.Fields.FirstOrDefault(f => f.Name == "ID");
        if (idField.Value == null) return null; // "OrDefault" = all-null object
        var match = _loggerARegex.Match(idField.Value);
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static ulong? ExtractGenericBot(Message msg)
    {
        // Embed, title is "Message Deleted", ID plain in footer.
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Footer == null || !(embed.Title?.Contains("Message Deleted") ?? false)) return null;
        var match = _basicRegex.Match(embed.Footer.Text ?? "");
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static ulong? ExtractBlargBot(Message msg)
    {
        // Embed, title ends with "Message Deleted", contains ID plain in a field.
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed == null || !(embed.Title?.EndsWith("Message Deleted") ?? false)) return null;
        var field = embed.Fields.FirstOrDefault(f => f.Name == "Message ID");
        var match = _basicRegex.Match(field.Value ?? "");
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static ulong? ExtractMantaro(Message msg)
    {
        // Plain message, "Message (ID: [id]) created by [user] (ID: [id]) in channel [channel] was deleted.
        if (!(msg.Content?.Contains("was deleted.") ?? false)) return null;
        var match = _mantaroRegex.Match(msg.Content);
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static FuzzyExtractResult? ExtractCarlBot(Message msg)
    {
        // Embed, title is "Message deleted in [channel], **user** ID in the footer, timestamp as, well, timestamp in embed.
        // This is the *deletion* timestamp, which we can assume is a couple seconds at most after the message was originally sent
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Footer == null || embed.Timestamp == null ||
            !(embed.Title?.StartsWith("Message deleted in") ?? false)) return null;
        var match = _carlRegex.Match(embed.Footer.Text ?? "");
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[1].Value),
                ApproxTimestamp = OffsetDateTimePattern.Rfc3339.Parse(embed.Timestamp).GetValueOrThrow()
                    .ToInstant()
            }
            : null;
    }

    private static FuzzyExtractResult? ExtractCircle(Message msg)
    {
        // Like Auttaja, Circle has both embed and compact modes, but the regex works for both.
        // Compact: "Message from [user] ([id]) deleted in [channel]", no timestamp (use message time)
        // Embed: Message Author field: "[user] ([id])", then an embed timestamp
        var stringWithId = msg.Content;
        if (msg.Embeds?.Length > 0)
        {
            var embed = msg.Embeds?.First();
            if (embed.Author?.Name == null || !embed.Author.Name.StartsWith("Message Deleted in")) return null;
            var field = embed.Fields.FirstOrDefault(f => f.Name == "Message Author");
            if (field.Value == null) return null;
            stringWithId = field.Value;
        }

        if (stringWithId == null) return null;

        var match = _circleRegex.Match(stringWithId);
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[1].Value),
                ApproxTimestamp = msg.Timestamp().ToInstant()
            }
            : null;
    }

    private static FuzzyExtractResult? ExtractPancake(Message msg)
    {
        // Embed, author is "Message Deleted", description includes a mention, timestamp is *message send time* (but no ID)
        // so we use the message timestamp to get somewhere *after* the message was proxied
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Description == null || embed.Author?.Name != "Message Deleted") return null;
        var match = _pancakeRegex.Match(embed.Description);
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[1].Value),
                ApproxTimestamp = msg.Timestamp().ToInstant()
            }
            : null;
    }

    private static ulong? ExtractUnbelievaBoat(Message msg)
    {
        // Embed author is "Message Deleted", footer contains message ID per regex
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Footer == null || embed.Author?.Name != "Message Deleted") return null;
        var match = _unbelievaboatRegex.Match(embed.Footer.Text ?? "");
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static FuzzyExtractResult? ExtractVanessa(Message msg)
    {
        // Title is "Message Deleted", embed description contains mention
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Title == null || embed.Title != "Message Deleted" || embed.Description == null) return null;
        var match = _vanessaRegex.Match(embed.Description);
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[1].Value),
                ApproxTimestamp = msg.Timestamp().ToInstant()
            }
            : null;
    }

    private static FuzzyExtractResult? ExtractSAL(Message msg)
    {
        // Title is "Message Deleted!", field "Message Author" contains ID
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Title == null || embed.Title != "Message Deleted!") return null;
        var authorField = embed.Fields.FirstOrDefault(f => f.Name == "Message Author");
        if (authorField == null) return null;
        var match = _salRegex.Match(authorField.Value);
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[1].Value),
                ApproxTimestamp = msg.Timestamp().ToInstant()
            }
            : null;
    }

    private static FuzzyExtractResult? ExtractGearBot(Message msg)
    {
        // Simple text based message log.
        // No message ID, but we have timestamp and author ID.
        // Not using timestamp here though (seems to be same as message timestamp), might be worth implementing in the future.
        var match = _GearBotRegex.Match(msg.Content);
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[1].Value),
                ApproxTimestamp = msg.Timestamp().ToInstant()
            }
            : null;
    }

    private static ulong? ExtractGiselleBot(Message msg)
    {
        var embed = msg.Embeds?.FirstOrDefault();
        if (embed?.Title == null || embed.Title != "🗑 Message Deleted") return null;
        var match = _GiselleRegex.Match(embed?.Description);
        return match.Success ? ulong.Parse(match.Groups[1].Value) : null;
    }

    private static FuzzyExtractResult? ExtractVortex(Message msg)
    {
        // timestamp is HH:MM:SS
        // however, that can be set to the user's timezone, so we just use the message timestamp
        var match = _VortexRegex.Match(msg.Content);
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[2].Value),
                ApproxTimestamp = msg.Timestamp().ToInstant()
            }
            : null;
    }

    private static FuzzyExtractResult? ExtractProBot(Message msg)
    {
        // user ID and channel ID are in the embed description (we don't use channel ID)
        // timestamp is in the embed footer
        if (msg.Embeds.Length == 0 || msg.Embeds[0].Description == null) return null;
        var match = _ProBotRegex.Match(msg.Embeds[0].Description);
        return match.Success
            ? new FuzzyExtractResult
            {
                User = ulong.Parse(match.Groups[1].Value),
                ApproxTimestamp = OffsetDateTimePattern.Rfc3339
                    .Parse(msg.Embeds[0].Timestamp).GetValueOrThrow().ToInstant()
            }
            : null;
    }

    public class LoggerBot
    {
        public ulong Id;
        public ulong ApplicationId;
        public string Name;

        public Func<Message, ulong?> ExtractFunc;
        public Func<Message, FuzzyExtractResult?> FuzzyExtractFunc;

        public LoggerBot(string name, ulong id, Func<Message, ulong?> extractFunc = null,
                         Func<Message, FuzzyExtractResult?> fuzzyExtractFunc = null,
                         ulong? applicationId = null)
        {
            Name = name;
            Id = id;
            FuzzyExtractFunc = fuzzyExtractFunc;
            ExtractFunc = extractFunc;
            ApplicationId = applicationId ?? id;
        }
    }

    public struct FuzzyExtractResult
    {
        public ulong User { get; set; }
        public Instant ApproxTimestamp { get; set; }
    }
}